Amniotic fluid is a protective fluid contained within the amniotic sac that surrounds a fetus during pregnancy. The amniotic fluid can provide a number of developmental benefits to the fetus. For example, amniotic fluid allows the fetus to move in the womb, which can facilitate proper bone growth and development. Further, the amniotic fluid helps provide a constant temperature about the fetus and helps provide protection against impact or sudden movements.
The amniotic fluid can also facilitate the exchange of proper nutritional and developmental components between the mother and the fetus to support proper organ development. However, the composition of amniotic fluid typically changes over time. For example, during early stages of pregnancy the amniotic fluid is often primarily an aqueous electrolyte solution. By about week 12 to week 14, amniotic fluid begins to contain a variety of proteins, carbohydrates, lipids, urea, and the like.
The volume of amniotic fluid also changes over the duration of the pregnancy. For example, the amount of amniotic fluid typically increases in volume up until about week 28 to week 34 of the pregnancy. At this point in the pregnancy, there is typically about 800 milliliters of amniotic fluid present in the amniotic sac. However, in some cases, the volume of amniotic fluid can decrease to an amount from about 400 milliliters to about 600 milliliters by about week 42.